It is known in the art that the combination of a capacitive coupling system and a nonlinear magnetizing inductance of the isolating transformer of a capacitor voltage transformer can cause a variety of nonlinear oscillations. This problem is discussed in the publication of KUMAR, B.S.A. and SUAT ERTEM, "Capacitive Voltage Transformer Induced Ferroresonance-Causes, Effects and Design Considerations" Electric Power Systems Research 21, (1991) 23-31. The problem of resonance discussed in the above-mentioned publication has not been solved in a simple and efficient manner.